Agreed with this. I used to work with an HD that would drive me nuts because he would be counting from the tower through a speaker at the front sideline. By the time the sound reached the battery in the back it was probably an eighth note off...

Adding in some bass drum clicks or simple beat patterns sometimes can help with getting rid of this. Analyze each set and decipher who has to be in charge of tempo audibly, while also who needs to be watching the drum majors. Watch the video the person below posted and also check out this link that has another video in addition to the one they posted below: https://drummajor.org/marching-band-sound-delay